Issue with Feigao 9L and BK 12020 ESC

[mpetrich]

I decided to clean-up the wiring on my 1/8th BL buggy and while I was doing some testing, I ran into a strange issue. I am using a 4s2p LiPo config with a UBEC. After I re-did all of my soldering (mostly to create cleaner joints), I moved the motor pinion away from the spur just to check how the motor was running. What I noticed was that under full throttle, the motor temp was reaching 130 degrees and after about five or six seconds of running WOT, the motor began to slow (the batteries were fully charged). I use the Nomadio radio and I have the battery voltage sensor installed. What I was able to see was that the voltage of the batteries were dropping about 1/2 volt every couple of seconds. There doesn't seem to be a short anywhere (I double checked) but I just thought it was really strange that the motor temp was so high with no load. Also, the fast drop in voltage in the batteries is telling me that something is not right. Finally, when I plug the batteries into the ESC (I am using Deans Connectors), I get a small spark. I never had that happen before but I also never used a 4s LiPo. Any ideas on what may be wrong or is this normal behavior when running the motor with no load?
Thanks for any help.
Matt